Humans lived in the region that is now Burma as early as 11,000 years ago, but archeological evidence dates the first settlements at about 2500 BCE with cattle rearing and the production of bronze. By about 1500 BCE, ironworks were in existence in the Irrawaddy Valley but cities, and the emergence of city-states, probably did not occur until the early years of the Common era when advances in irrigation systems and the building of canals allowed for year-long agriculture and the consolidation of settlements, although local mythology dates back to c. 1000-600 BC with the immigration of some people from janapadas, ancient countries in modern-day India.